Is 3wks. to long not to start car?

I replaced the AC Delco battery with an Optima red top about 6 months ago before I stored it for the winter. I've been starting my car and letting it run for about 30 minutes, and or, driving it for 15 to 20 miles every week. Well, every week eventually turned into every other week, then every 3 weeks. I leave the battery as is between start-ups (I know I should at least disconnect the negative cable, but I always intend to be back sooner than 3 weeks). The last time I started my car, it cranked then paused for a split second, then started. The volt gauge in the car read about 14 volts, so I assumed that the overnight temp in N.Y. was too cold lately for 3 week intervals of start-ups. But today, 3 weeks later, I couldn't even disengage the alarm. Turned the key once to see if I had any power and the volt gauge read 8 volts. I had to jump it. While it was running, I checked the volt gauge and it read about 14 volts. So I took a 20 mile spin, came home, shut it down, did some paper work in the bathroom (took like 45 minutes) and my car started like normal. Is 3 weeks too long not to start my car? I figured that a new Optima red top would be efficient for 3 week start-up intervals without disconnecting it or using a charger. Or could I have a problem other than being lazy for not using a charger or disconnecting the negative cable?

I've gone more than 3 weeks without starting the car on my other f-body several times over the winter, and it always starts right up whenever I finally get a chance to take it for a drive. Also important to note, it's not a new battery either. I've had this battery in the car for at least 3 years-maybe longer-as it is the same one installed from when I purchased the car...

Mine has been sitting for 3 weeks as is.
On jackstands.
Will probably be roughly 3 more weeks before it is back on the road.

Should be fine.